This invention relates to a motor that is operated by controlled expansion of a pressurized gas. The motor includes a rotor that has a helical screw configuration for conveying pressurized gas from an inlet chamber to an outlet chamber. The helical passage defined by the screw has a progressively increasing cross section, measured from the inlet to the outlet, whereby the gas expands as it travels along the passage. Expansion of the gas produces rotary motion of the rotor.
A principal aim of the invention is to provide a gas expansion motor that has a relatively small diameter, thus reducing the need for precise dynamic balancing of the rotor. Another aim of the invention is to provide a gas expansion motor wherein the rate of gas expansion is controlled by the rotor passage configuration. A further aim of the invention is to provide a motor wherein the gas can expand from a relatively high pressure to a relatively low pressure (near atmospheric) in a single turbine stage. An important object of my invention is to provide a gas expansion motor which operates with a minimum of turbulence and pressure loss. A general object of the invention is to provide a gas expansion motor that can be manufactured at relatively low cost.